Just to add yet another wrinkle (I guess I'm just bringing up more problems rather than solving them; sorry about that), sometimes the person trying to get help here doesn't even know what "Let's Encrypt" is and isn't trying to set up a server, but keeps seeing an error message on their phone, and by clicking around the only text they can find about what it is says "Let's Encrypt" so they find their way here. They often don't even recognize the hostname that it says there's a failure connecting to, and if it's something like in their phone's email settings it just "pops up" no matter what they're doing so they don't know what causes it. Sometimes the issue is that it's actually malware on their phone for which the certificate stopped working, so when they come here asking about it people here go about trying to help them fix the server when that's not actually what they need help with at all.
Some of this is perhaps UI on the phone could be a lot better, but until that happens we might need some way to determine whether somebody here is even trying to set up a server or not.
For some example threads where people weren't trying to set up a server but were just confused by their phone's messaging (sometimes leading to confusion on the part of those trying to help as well): Let's Encrypt got on my iphone without permission, Help Pop Up Message, Newbie trying to understand.